An implant for insertion into the body is known from DE 299 24 228 U1. The implant concerned is a stent for prophylaxy of a restenosis of a vessel. In general stents are inserted into hollow vessels, such as blood vessels or body openings for example, in order to open these out and keep them in their expanded state. Usually catheters and guide wires are employed to insert the stent.
In coronary angiography the localization of the stent with reference to x-ray images of the body tissue is also known. Stents which are manufactured from materials with a low x-ray absorption sometimes cannot be made visible or cannot be made sufficiently visible for radiographical purposes in the body tissue.
To determine the position of the stent it is also normal to localize the catheter or guide wire with reference to x-ray markers applied to it. One disadvantage of this method is that the position of stents which cannot be localized radiographically after removal of the catheter or of the guide wire can no longer be determined.
Furthermore it is necessary to record a plurality of x-ray images for localization on introduction of the stent into the vessel. This subjects both the patient and also the medical personnel to a high dose of radiation.
An imaging method is known from EP 0 885 594 B1 in which ultrasound images can be recorded by means of a catheter to be introduced into the vessel. The ultrasound images serve as an aid for introducing and positioning the stent in the vessel. A disadvantage of this method is that the catheter used for ultrasound imaging has to be removed from the vessel before the stent is inserted. The position of the stent cannot be traced while it is being inserted.
A catheter with a localizable end area is known from DE 42 15 901. A coil is accommodated in the end area. A magnetic field can be generated with the coil. The position of the end area is determined with reference to the magnetic field distribution of the magnetic field. A disadvantage is that the measurement device used for this must be arranged in a screening chamber. Furthermore, to feed electrical energy to the coil to generate the magnetic field, the catheter must always be connected to a supply lead. This significantly restricts the handling capabilities of the catheter.
A device for determining the position of an end area of a catheter is known from U.S. Pat. No. 6,233,476 B1. Magnetic field strengths measured by Hall sensors are used to determine the position. A disadvantage of the known device is that the catheter can only be employed in few special medical applications. Furthermore the accuracy of the position determination is very badly affected by metallic objects located in the vicinity of the end area.